Photo Illustration by Sarah Rogers/The Daily Beast/GettyBeto O'Rourke and John Cornyn were not often on the same page during the six years that they both represented Texas in Congress. But for a brief moment, O'Rourke—then a Democratic congressman from El Paso and now a 2020 presidential hopeful—got the powerful Republican senator behind him in his quest to stop the federal government from building a wall on the U.S.-Mexico border.

The effort ultimately proved for naught, as a barrier ended up being built at the contested site. But O'Rourke's successful wooing of the No. 2 Republican in the Senate could prove to be an asset as he goes about pitching himself to primary voters: proof that on Donald Trump's signature issue, he not only has spent years crafting his position but also has some bipartisan credibility to bring to the debate.

The collaboration with Cornyn came in 2013, as U.S. Customs and Border Protection made plans to build a $5.5 million, 17-foot high steel fence along a half-mile portion of the border in El Paso, a city that is separated from Mexico by the Rio Grande and, in most places, high steel walls. At the time, that type of barrier did not exist in this historic part of the city, where Spanish explorers first crossed the river north in 1598.